|Publication number||US8212412 B1|
|Application number||US 12/325,814|
|Publication date||Jul 3, 2012|
|Filing date||Dec 1, 2008|
|Priority date||Nov 30, 2007|
|Publication number||12325814, 325814, US 8212412 B1, US 8212412B1, US-B1-8212412, US8212412 B1, US8212412B1|
|Inventors||Eric L. Benedict, Nicholas P. Borland, Magdelena Dale, Belvin Freeman, Kim A. Kite, Jeffrey K. Petter, Brendan F. Taylor|
|Original Assignee||Northern Power Systems Utility Scale, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (12), Referenced by (6), Classifications (26), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 60/991,500, filed Nov. 30, 2007, and titled Voltage Ramp Method for Connecting a Power Converter to Multiple Independent Large Capacitors at Unknown Voltages, which is incorporated by reference herein in its entirety.
This invention was made with State of California support under California Energy Commission Agreement number 500-04-011. The Energy Commission has certain rights to this invention.
The present invention generally relates to the field of power systems. In particular, the present invention is directed to a system for connecting a plurality of energy storage devices with a variable voltage power source such as a power converter.
Power systems that use power converters or other variable voltage power sources and energy storage devices, such as capacitors or batteries, experience challenges when attempting to charge a energy storage device that already contains a charge that is either unknown or different than the power converter's output voltage. If connected haphazardly, a large and potentially damaging current surge may result. Several approaches in the prior art have attempted to eliminate the possibility of a dangerous current surge.
One method is to discharge the energy storage device to a zero voltage level and then connect the energy storage device to the power converter when the power converter has an output voltage of zero volts. However, this method generally results in a waste of energy since the energy storage device's charge is generally discharged without being applied to a load.
Alternatively, a resistor can be placed in parallel with the energy storage device. The resistor restricts the current traveling between the power converter and the energy storage device, thus avoiding a current surge. However, this approach has two shortcomings. First, it is time consuming to wait for the energy storage device to achieve the same voltage as the power converter. Second, the resistor, while controlling the current, generates heat as a byproduct of the current passing through it. Thus a system built with a resistor, while workable, also tends to waste power.
One aspect of the present invention is a system for connecting first and second energy storage devices to a power converter, where the first energy storage device initially has a first voltage and the second energy storage device initially has a second voltage. The system comprises a power converter that provides power having an output voltage that changes over time, a first switch for connecting the first energy storage device with the output voltage of the power converter in response to a first signal, a second switch for connecting the second energy storage device with the output voltage of the power converter in response to a second signal, and a controller. The controller is connected to the power converter and to the first and second switches. The controller compares the first voltage of the first energy storage device with the output voltage of the power converter and generates the first signal when the output voltage and the first voltage are substantially equal. The controller also compares the second voltage of the second energy storage device with the output voltage and generates the second signal when the output voltage and the second voltage are substantially equal.
Another aspect of the present invention is a controller for a system for supplying power. The system includes a variable voltage power source having an output voltage, first and second energy storage devices, each having an initial voltage, and first and second switches for connecting, respectively, the variable voltage power source with the first and second energy storage devices. The controller comprises a first sensing device for measuring the difference between the output voltage of the variable voltage power source and the voltage of the first energy storage device and providing a first measurement signal containing information representing the difference, a second sensing device for measuring the difference between the output voltage of the variable voltage power source and the voltage of the second energy storage device and providing a second measurement signal containing information representing the difference, and a logic unit for evaluating the first measurement signal and for generating a first switching signal when the information in the first measurement signal indicates the output voltage of the power source and the voltage of the first energy storage device are substantially equal. The logic unit also evaluates the second measurement signal and generates a second switching signal when the information in the second measurement signal indicates the output voltage of the power source and the voltage of the second energy storage device are substantially equal.
Another aspect of the present invention is a method of connecting a plurality of energy storage devices to a variable voltage power source that provides power having an output voltage. The method comprises changing the voltage of the power provided by the variable voltage power source until it substantially equals the voltage of a first one of the plurality of energy storage devices, connecting the first one of the plurality of energy storage devices to the output voltage of the variable voltage power source, continuing to change the output voltage of the power provided by the variable voltage power source until it substantially equals the voltage of a second one of the plurality of energy storage devices, and connecting the second one of the plurality of energy storage devices to the power source.
For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:
Referring to the drawings,
A general description of power system 100 as it relates to
Switch 124 may, for example, be a contactor, other electro-mechanical switching device, a solid state switch or other switches capable of handling large power loads at relatively fast switching rates, e.g., rates of tens of milliseconds or faster. Switch 124 may be implemented as two switches, one for connecting power converter 108 via line 110′ with energy storage device 104 and a second for connecting power converter 108 via line 110″ with energy storage device 104. Alternatively, switch 124 may be implemented as a single two-part switch, with one part for connecting power converter 108 via line 110′ with energy storage device 104 and a second part for connecting power converter 108 via line 110″ with energy storage device 104. Each switch 124, when implemented as two switches, or each part of switch 124, when implemented as a single two-part switch, may be independently operable so as to open and close in response to a unique switching signal. Alternatively, switch 124 may be implemented so that one switching signal causes both switches (when implemented as two separate switches) or both parts of the switch (when implemented as a single two-part switch) to open or close. In another implementation of power system 100, a single storage sensor, either storage sensor 116 or 120, may be used, which single storage sensor may be connected (not shown) to measure the voltage across one of the two switches in switch 124 (when implemented as two switches) or across one part of switch 124 (when implemented as a single two-part switch).
Storage controller 102 includes a logic unit 126 that compares the voltage between storage sensor 116 and supply sensor 120. Depending upon desired implementation, and as described more below, when logic unit 126 determines that the voltages measured by sensors 116 and 120 are the same, storage controller 102 sends a switching signal to switch 124 on control line 128. Alternatively, when the voltage difference measured by sensors 116 and 120 is small enough to allow connection of power converter 108 with energy storage device 104 with no current surge or a current surge that is acceptably small (i.e., when the voltages are substantially equal), storage controller 102 sends a switching signal to switch 124 on control line 128. In response to the switching signal, switch 124 closes, thereby connecting energy storage device 104 with power converter 108. When a single sensor 116 or 120 is connected to measure the voltage across one of the switches of switch 124 (when implemented as two switches) or across one part of switch 124 (when implemented as a single two-part switch), logic unit 126 may determine the voltage difference between energy storage device 104 and power converter 108 using the voltage measurement provided by the single sensor. In operation, logic unit 126 first closes one of the two switches in, or one part of, switch 124, and then measures the voltage across the open one of, or part of, switch 124. When the voltage across the open one or part of switch 124 is substantially zero, logic unit 126 will close the open one or part of switch 124, thereby connecting energy storage device 104 with power converter 108. It is understood that yet other alternative ways to measure the voltage across energy storage device 104 and on line 110 are available. In any event, measurement of the voltages will allow logic unit 126 to know when the voltage difference between energy storage device 104 and line 110 are substantially equal and thus capable of being connected without a current surge or a current surge that is acceptably small. What defines a “substantially equal” voltage will be influenced by the extent of current surge that can be accommodated by the element(s) of system 100 that is least tolerant of a current surge. In certain implementations this current surge may be one percent or less, while in other applications a current surge of five percent or more could be tolerated.
Energy storage devices 104 may take on many forms known in the art including, but not limited to, capacitors, batteries, fuel cells, or superconducting magnetic energy storage devices. In one example, energy storage device 104 is a battery or a string of batteries. In another embodiment, energy storage device 104 is a plurality of capacitors or supercapacitors, often referred to as a “bank” of capacitors. In an exemplary embodiment, energy storage device 104 includes sixteen banks of sixteen capacitors.
Power converter 108 converts power from alternating current (AC) to direct current (DC) or from DC to DC. For convenience, the term “power converter” is intended to encompass conventional power converters and any other variable voltage power sources unless the context of use clearly indicates otherwise.
The embodiment of power system 100 illustrated in
In addition, power system 100 may include a power controller 138 having a logic unit 140. Power controller 138 controls the operation of power converter 108 and in certain implementations communicates with storage controllers 102 via line 144 in connection with the overall control of power system 100. Alternatively, in certain implementations, storage controllers 102, and storage controller 204 discussed below, may form part of power controller 138. Power controller 138 and storage controllers 102 may also operate autonomously if desired, and for this reason line 144 is depicted in dotted form indicating it is an optional feature.
Power system 200 may include power controller 138 having logic unit 140. In certain implementations storage controller 204 may form part of power controller 138. Alternatively, power controller 138 may communicate with storage controller 204. In another embodiment, power controller 138 and storage controller 204 may operate autonomously.
By way of example and as illustrated in
The voltage at which an energy storage device 104 connects to power converter 108 will, in certain applications, be equal to the initial voltage of the energy storage device. In other applications, however, it may be desirable for energy storage device 104 not to connect with power converter 108 at the energy storage device's initial voltage, but instead at a slightly lower or advance voltage. An advance voltage is selected to take into account the processing time of storage controller 102, the time necessary to close switch 124 and the rate of the voltage increase, e.g., the slope of voltage line 304. Thus, with reference to
As shown in
Discussing in somewhat more detail the example shown in
Discussing now in somewhat more detail the operation of storage controller 102, logic unit 126 operates according to a storage controller logic 600 as shown in
When the output voltage is increased at a non-linear rate, as in
It may be desirable in certain situations to add more energy storage devices 104 to power converter 108 after power converter 108 has, for example, already reached ending voltage 406 as shown in
Alternatively, there may be times when the output voltage of power converter 108 may increase too fast to connect energy storage device 104 or when storage controller 102 or power controller 138 or both may not properly initiate a connection. In any event, logic unit 140 or logic unit 126 may store and compare the measured voltages of energy storage devices 104 with the output voltage from power converter 108 to determine whether an energy storage device 104 has been missed, i.e., output voltage is greater than the initial voltage of energy storage device 104. If energy storage device 104 has failed to connect, power controller 138 or storage controller 102 may disconnect any already connected energy storage devices 104 and follow the procedure discussed in reference to
Other control logic than that illustrated in
In an alternative embodiment, power controller 138 has the additional capability to identify current increases resulting from the addition of other energy storage devices 104. In yet another embodiment, power controller 138 has the ability to identify and report the number of current step increases and therefore is able to determine the number of energy storage devices 104 connected to power converter 108. By tracking the current or number and sizes of current steps, power controller 138 is able to identify the number of energy storage devices 104 present in the system with no other explicit configuration information. Knowledge of the number of energy storage devices 104 may simplify and enable the self-configuration of an energy storage system with multiple independent building blocks.
Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3566151 *||Mar 10, 1969||Feb 23, 1971||Pilkington Brothers Ltd||Temperature control circuits|
|US5546003 *||Mar 7, 1994||Aug 13, 1996||Polytronics Engineering Ltd.||Multi-cell battery monitoring system with single sensor wire|
|US5623195 *||Jun 22, 1994||Apr 22, 1997||Lucent Technologies Inc.||Apparatus and method for controlling a charging voltage of a battery based on battery temperature|
|US5784626 *||Jul 26, 1995||Jul 21, 1998||International Business Machines||Battery connecting device for a computer system and a method of switching batteries|
|US6396170 *||Mar 29, 2000||May 28, 2002||Powerware Corporation||Method and apparatus for coordinating uninterruptible power supply modules to provide scalable, redundant power|
|US6430692 *||Sep 25, 1998||Aug 6, 2002||International Business Machines, Corporation||Series-parallel battery array conversion|
|US6885879 *||Jun 2, 2000||Apr 26, 2005||Astec International Limited||Battery reconnect system for a telecommunications power system|
|US20050046386 *||Aug 18, 2004||Mar 3, 2005||Junji Nishida||Battery pack charging apparatus and method|
|US20050134230 *||Nov 12, 2004||Jun 23, 2005||Hideyuki Sato||Battery pack, battery protection processsing apparatus, and control method of the battery protection processing apparatus|
|US20060267551 *||Jan 3, 2006||Nov 30, 2006||Sehat Sutardja||Medical device|
|US20080036423 *||Aug 10, 2007||Feb 14, 2008||Denso Corporation||Method and apparatus for managing charge/discharge current of on-vehicle battery to control on-vehicle generator in consideration of offset of charge/discharge current|
|WO2006098157A2 *||Feb 23, 2006||Sep 21, 2006||Toyota Jidosha Kabushiki Kaisha||Monitoring device for power supply system|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8866441 *||Nov 10, 2010||Oct 21, 2014||Atieva, Inc.||Interlock mechanism for a multiple battery pack|
|US9325038 *||Jul 3, 2013||Apr 26, 2016||Samsung Sdi Co., Ltd.||Temperature controlling system and method for battery|
|US9356323 *||Jul 3, 2013||May 31, 2016||Samsung Sdi Co., Ltd.||Temperature controlling system and method for battery|
|US20110111268 *||Nov 10, 2010||May 12, 2011||Sam Weng||Interlock Mechanism for a Multiple Battery Pack|
|US20120217932 *||Feb 22, 2012||Aug 30, 2012||Torqeedo Gmbh||Connecting electrical storage devices in parallel|
|US20140197778 *||Jul 3, 2013||Jul 17, 2014||Samsung Sdi Co., Ltd.||Temperature controlling system and method for battery|
|U.S. Classification||307/87, 307/31, 320/162, 307/23, 320/134, 307/113, 320/136, 307/84, 307/85, 307/64, 320/125, 320/165, 307/66, 320/126|
|International Classification||H02J3/00, H02J1/00|
|Cooperative Classification||Y10T307/344, Y10T307/406, Y10T307/724, Y10T307/625, Y10T307/718, Y10T307/747, Y10T307/615, Y10T307/735, H02J2001/006, H02J1/10|
|Mar 10, 2009||AS||Assignment|
Owner name: NORTHERN POWER SYSTEMS, INC., VERMONT
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BENEDICT, ERIC L.;BORLAND, NICHOLAS P.;DALE, MAGDELENA;AND OTHERS;SIGNING DATES FROM 20090227 TO 20090305;REEL/FRAME:022371/0134
|Dec 16, 2011||AS||Assignment|
Owner name: WIND POWER HOLDINGS, INC., VERMONT
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:NORTHERN POWER SYSTEMS, INC.;REEL/FRAME:027403/0650
Effective date: 20110701
Owner name: NORTHERN POWER SYSTEMS UTILITY SCALE, INC., VERMON
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:WIND POWER HOLDINGS, INC.;REEL/FRAME:027403/0657
Effective date: 20110701
|Mar 18, 2014||AS||Assignment|
Owner name: NORTHERN POWER SYSTEMS, INC., VERMONT
Free format text: MERGER;ASSIGNOR:NORTHERN POWER SYSTEMS UTILITY SCALE, INC.;REEL/FRAME:032461/0921
Effective date: 20131231
|Dec 4, 2015||FPAY||Fee payment|
Year of fee payment: 4